Downhole drilling compositions and methods of preparation

ABSTRACT

The invention provides a method of altering the properties of a drilling fluid by adding effective amounts of crushed or whole oilseeds or mixtures of crushed whole oilseeds to a drilling fluid. The crushed or whole oilseeds or mixture of crushed or whole oilseeds are selected to impart any one of or a combination of effects including but not limited to: an increase in drilling fluid emulsion stability in oil-based or invert emulsion fluids, decreased specific gravity of the drilling fluid, seepage loss control, filtration control, oil wetting and deflocculation/dispersion, of entrained solids and/or reduced torque and drag of the drilling string.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/699,634, filed Jul. 15, 2005 and U.S. Provisional ApplicationSer. No. 60/718,852, filed Sep. 20, 2005, the entire disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The invention provides a method of altering the properties of a drillingfluid by adding effective amounts of crushed or whole oilseeds ormixtures of crushed whole oilseeds to a drilling fluid. The crushed orwhole oilseeds or mixture of crushed or whole oilseeds are selected toimpart any one of or a combination of effects including but not limitedto: an increase in drilling fluid emulsion stability in oil-based orinvert emulsion fluids, decreased specific gravity of the drillingfluid, seepage loss control, filtration control, oil wetting anddeflocculation/dispersion of entrained solids and/or reduced torque anddrag of the drilling string.

BACKGROUND OF THE INVENTION

Drilling fluid circulating systems are employed during downhole drillingoperations to provide a number of functions. These functions includeproviding cooling to the drill bit, removing drilled cuttings to thesurface and providing a hydrostatic head to the formation to prevent theescape of oil and gas from the well.

As is well known, in almost all drilling operations, drilling fluid iscontinuously lost to the formation during the drilling process due toseepage of the drilling fluid into the formations. Seepage will occur atvarying rates depending on the relative porosity or fractures of theformation and the hydrostatic head pressure. While some seepage willalways occur, generally it is necessary to control drilling fluid lossin order to ensure effective drilling fluid circulation and to reducedrilling fluid costs. Notwithstanding efforts to prevent drilling fluidlosses, tens of thousands of cubic meters of these fluids are lost eachyear.

There are generally two classes of drilling fluids namely water-basedand oil-based drilling fluids. Water-based drilling fluids are generallyless expensive than oil-based drilling fluids but cannot be usedeffectively in all formations and may result in operational problems incertain formations such as hydratable shales, silts or clays. In theseformations, there is a tendency for the hydratable materials todestabilize the wellbore as well as disperse within the drilling fluid.The dispersion effect causes substantial increases in the solids contentof the drilling fluid and leads to various problems including solidsseparation difficulties at the surface and detrimental increases to theviscosity of the fluid.

In order to overcome these difficulties associated with water-baseddrilling fluids, drilling fluids comprised of oil or water-in-oil (a.k.ainvert emulsions) are often used. Generally, emulsion compositions inwhich oil remains the predominant or continuous phase are preferred. Inorder to maintain effective and stable emulsions, the compositions willrequire the use of emulsifiers to stabilize the emulsion. Such emulsionsare effective in stabilizing hydratable shale or clay formations.

It is also well known that seepage losses can be mitigated through theaddition of fibrous materials into the drilling fluid such as sawdust,fabrics, nut hulls, seed hulls and minerals such as ground limestone.These materials can bridge the various loss zones where fluids are beinglost by mixing with drilled cuttings, and “viscosifiers” to create a“filter-cake” that may significantly reduce fluid losses to theformation. Examples of the use of various plant derived components asdrilling fluid additives include U.S. Pat. No. 6,323,158, U.S. Pat. No.5,763,367, U.S. Pat. No. 5,599,776, U.S. Pat. No. 2,691,629, U.S. Pat.No. 6,750,179, U.S. Pat. No. 4,439,328, U.S. Pat. No. 5,076,944, U.S.Pat. No. 5,861,362, United States Patent Number 2004/0014609 and UnitedStates Patent Applications 2004/0063587 and 2004/00232816. In the past,any plant materials have generally been preprocessed to remove any oilsand gums associated with the plant material.

Typically, these materials also have a detrimental effect on thedrilling fluid and may significantly change the properties of the fluidby increasing viscosity to unmanageable levels or de-stabilizing theemulsion. These effects directly impact the efficiency of surfacepumping and solids removal equipment as well as causing wellboredestabilization. In the particular case of fibrous and granularmaterials including but not limited to cardboard, nut shells, calciumcarbonate, and sawdust, within invert emulsions, these materials will bebroken down over time to smaller sizes resulting in an increase in therelative surface area of these materials within the emulsion. The neteffect of this size breakdown and the hydrophilic nature of thesematerials will contribute to the breakdown of the emulsion. As a result,over time, additional emulsifiers and oil-wetting agents must be addedto the emulsions to maintain the emulsion properties, which againcontribute to the cost of the drilling fluid. In the specific case ofadding limestone or other mineral based seepage control agents to thedrilling fluid, the specific gravity of the drilling fluid is alsoincreased which increases the hydrostatic pressure within the wellborewhich may directly increase the seepage losses and also requiresstronger pumping equipment.

Other functional requirements of drilling fluids, problems that may beencountered with the use of drilling fluids and past solutions arebriefly discussed below:

Drilling fluid systems also require the use of torque reducing and dragreducing agents to relieve both rotational twist that builds up in thedrilling pipe during rotation and the frictional forces required to liftthe drill string from the borehole through the drilling fluid. In thepast, the use of spherical media such as glass beads, Teflon beads,styrene-divinylbenzene copolymer beads, walnut hulls, and oil basedadditives (petroleum or vegetative) within the drilling fluid havedemonstrated the ability of these additives to relieve rotational twistand reduce drag.

Drilling fluids also preferably require materials to disperse entraineddrilled solids that build up in the drilling fluid system during theexcavation process. In many systems, the materials used are surfactantsand phenolic compounds including lignins and tannins.

Filtration control agents may be added to both water and oil-baseddrilling fluids to reduce the penetration of the drilling fluid intoformation rock media. The addition of colloidal, polymeric and colloiddispersing chemicals like surfactants, emulsifiers, lignite and/orlignosulphonate materials may be used.

In both oil and water based drilling fluids, emulsifiers may be added toaid the emulsification of oils added to water based fluids and wateradded to oil-based fluids. Emulsifiers also act as surfactants in bothwater based and oil based drilling fluids. Typically this effect isobserved as a reduction in the viscosity of the treated fluid. Theeffect is caused by the adsorption of the emulsifier onto the surface ofan entrained particle or emulsified phase component which enhancessteric hindrance to flocculation between dispersed molecules. Generally,the addition of emulsifiers is dictated by the requirements of the fluidfor the level of dispersion of secondary phase and/or entrained solidsin the fluid system.

In the past, emulsifiers have been prepared using crude tall oil fattyacids (CTOFA) derived from Kraft pulp-making processes. CTOFA's areoften used as the source of fatty acids for creating soaps/emulsifiersin oil-based drilling fluids. CTOFAs are normally considered to be awaste product and as a result, the price of CTOFAs is relatively low (inthe range of $310/metric ton). The chemical composition of CTOFAs isprimarily C18 oleic and linoleic acids in addition to relatively highconcentrations of resins including abietic, dehydroabietic, palustric,isopalustric, isopimaric, neoabietic and pimaric acids. CTOFAs are veryviscous and must typically be diluted with solvents in order to beefficiently mixed within a drilling fluid.

Some invert emulsions are blended with purified phospholipids to assistin oil wetting and dispersion of hydrophilic materials (drilledcuttings, barite and the like) which become entrained in the fluid.Purified phospholipids are used sparingly due to the high cost(typically in the range of $1000/ton).

In comparison, oil seeds are characterized by a much wider range offatty acids with chain lengths that typically range from C14-C24 andnaturally contain phospholipids. Different oilseeds contain verydifferent specific compositions of fatty acids and phospholipids. From acost perspective whole or crushed oilseeds are also in the same range asCTOFAs. However, any purified oilseed fatty acid is expensive (in therange of $1000+/ton).

While many solutions to the requirements of drilling fluids have beenprovided, there continues to be a need for enhanced drilling fluidcompositions, while maintaining functionality to effectively bridgefractures and other loss zones. In particular, there has been a need fordrilling fluid compositions having lipophilic/oleophilic characteristicsto assist in dispersing the drilling fluid as the drilling fluid isbroken down. Still further, there has been a need for drilling fluidcompositions with increased stability where the stability of thedrilling fluid is enhanced through delayed release of emulsifyingagents.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a method of alteringthe properties of a drilling fluid comprising the step of adding aneffective amount of crushed or whole oilseeds or a mixture of crushed orwhole oilseeds to a drilling fluid, the crushed or whole oilseeds ormixture of crushed or whole oilseeds selected to impart any one of or acombination of: an increase in drilling fluid emulsion stability inoil-based or invert emulsion fluids, decreased specific gravity of thedrilling fluid, seepage loss control, filtration control, oil wetting,deflocculation/dispersion of entrained solids, reduced drag and rotarytorque reduction. Oilseeds may be selected from any one of or acombination of canola, flax, sunflower, cotton, castor, soya, hemp,sunflower, safflower, grape, palm kernel, lesquerella, corn, peanut,mustard, poppy, sorghum, and sesame seeds.

In one aspect of the invention, oilseeds are added to a concentration of3-150 kg/m³ of drilling fluid and in more specific embodiments, oilseedsare added to a concentration of 10-60 kg/m³ of drilling fluid or 45kg/m³ of drilling fluid.

In one embodiment, whole oilseeds or a mixture of whole oilseeds areadded to the drilling fluid immediately prior to circulating thedrilling fluid downhole.

In accordance with another embodiment, the invention provides a methodof stabilizing a drilling fluid emulsion comprising the step of addingan effective amount of whole oilseeds or a mixture of whole oilseeds toa drilling fluid emulsion.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described by the following description and the drawingswhere:

FIG. 1 is a graph showing the change in viscosity for different drillingfluid samples with and without oilseeds;

FIG. 2 is a bar graph showing the effect of crushed mustard seed on adrilling fluid containing an organophilic clay; and,

FIG. 3 is a graph showing the effect of crushed mustard seed on therheology of a base drilling fluid.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, drilling fluid compositions containingcrushed or whole oilseeds are described in which the properties of thedrilling fluids can be engineered based on the properties of crushed orwhole oilseeds or mixtures of crushed or whole oilseeds. Fluidproperties include but are not limited to an increase in drilling fluidemulsion stability in oil-based or invert emulsion fluids, decreasedspecific gravity of the drilling fluid, seepage loss control, filtrationcontrol, oil wetting, deflocculation/dispersion of entrained solids andreductions in torque and drag in the drillstring.

Within the context of the invention, filtration control is a measure ofseepage control and is a measurable parameter based on the passage ofdrilling fluid through an engineered medium over a fixed period of time(as defined by the American Petroleum Institute). Filtration control isdramatically affected by the continuous phase viscosity and theultrafine solids dispersed in the drilling fluid. Emulsion stability isdetermined by the size of emulsion droplets in the continuous phase aswell as the degree of dispersion of molecular and ultrafine drilledsolids as stabilized by any surfactant. Seepage loss is more concernedwith macro size material. The sizing and optimization of seepage lossmaterials is described at great length in existing prior art.

Oilseeds including but not limited to canola, flax, sunflower, cotton,castor, soya, hemp, sunflower, safflower, grape, palm kernel,lesquerella, corn, peanut, mustard, poppy, sorghum, and sesame arerepresentative examples of oilseeds that may be utilized in accordancewith the invention to engineer the fluid properties of oil or waterbased drilling fluid emulsions.

Different oilseeds have different surface structural/mechanicalproperties and different chemical characteristics that can be utilizedto impart various properties to a drilling fluid either as singlecomponent or as a mixture of seeds (crushed or whole). Spherical seedsand flax seeds exhibited the best reductions in torque and drag.

Structural/mechanical characteristics include the shape, size andsurface texture of the seed and may be utilized to affect the viscosityof the drilling fluid and, in particular, the torque and drag reducingcharacteristics of the drilling fluid.

Chemical characteristics include the seed composition and in particular,the hydrocarbon composition of the seeds. The typical structuraldimensions, shape and texture of flax, sesame, canola and mustard seedsare shown in Table 1.

TABLE 1 Typical Structural Dimensions, Shape and Texture of SelectOilseeds Oil Seed Components Typical values Seed Type Flax Sesame CanolaMustard Size 5 mm × 1 mm 1.5 mm 2 mm 0.25 mm Shape Flat Flat SphericalSpherical Tear Tear Surface Glassy Smooth Smooth Smooth TextureTypical hydrocarbon properties of oil seeds and crude tall oil fattyacids are shown in Tables 2 and 2A.

TABLE 2 Typical Hydrocarbon Properties of Oil Seeds and Crude Tall OilFatty Acids (CTOFAs) Fatty acid Canola Castor Lesquerella Linseed MaizeMustard Olive C6:0 <0.1% C8:0 <0.1% C10:0 <0.1% C12:0 <0.1% C14:0 0.1%<0.1% C14:1n-5cis C16:0 3.5% 1.3% 6.3% 11.4% 2.8% 8–21%  C16:1n-7cis0.2% 0.7% 0.1% 0.1% 0.2% 1–4% C16:4n-3 C18:0 1.5% 2.1% 4.1% 1.9% 1.5%1–6% C18:1n-9cis(12-OH) 87.6% C18:1n-9cis 60.1% 18.1% 18.0% 25.3%  21%53–80%  C18:1n-7 C18:2n-6cis 20.1% 9.3% 16.0% 60.7%  21% 2–24%  C18:3w614.0% C18:3n-3cis 9.6% 57.0% 12.5%  1–2% C18:4n-3 C20:0 0.6% 0.2% 0.1%1.0% <0.5%  C20:1n-11  12% C20:1n-11cis(14-OH) 51.4% C20:1n-9cis 1.4%1.2% 0.1% <0.5%  C20:4n-6cis C20:4w3 C20:5n-3cis (EPA) C21:5w3 C22:01.3% 0.1% 0.4%  <1% C22:1n-9cis 0.2%  22% C22:5n-3cis C22:5n-6cisC22:6n-3cis (DHA) C24:1n-9cis Total Saponifiables 98.6% 101.8% 99.4% Oilcontent % wt/wt 42.0% 25.0% Oil $CDN/MT $720 $1,980 $790 Seed $CDN/MT$1,320 Seed Oil Content 42.0% 41.0% 30.0%  Phytosterols 0.53–0.97%Brassicasterol 0.104% 0.240% Campesterol 0.207% 0.131% Stigmasterol0.004% 0.035% β-Sitosterol 0.392% 0.273% Δ5-Avenasterol 0.014%Δ7-Avenasterol 0.001% Δ7-Stigmasterol 0.017% Tocopherols α 0.027% 0.038%0.003% β 0.000% γ 0.042% δ 0.000% 0.047% Total Unsaponifiables 0.8% 0.7%Palm Fatty acid kernel Peanut Sesame Safflower Soya Sunflower C6:0 C8:03–4% C10:0 3–7% C12:0 46–52%  C14:0 15–17%  — 0.1% C14:1n-5cis C16:06–9% 8–13%  8–11%   6–7% 10.8% 6.2% C16:1n-7cis <0.3% <0.3% <0.5% 0.2%0.2% C16:4n-3 C18:0 1–3%  1–4%  4–6%  2–3% 4.0% 4.7% C18:1n-9cis(12-OH)C18:1n-9cis 13–19%  35–66%  37–42%  10–20%  23.8% 20.4% C18:1n-7C18:2n-6cis 0.5–2%   14–41%  39–47%  68–80%  53.3% 68.8% C18:3w6C18:3n-3cis <0.3% <0.5% 7.1% C18:4n-3 C20:0   <2%   <1% <0.5% C20:1n-11C20:1n-11cis(14-OH) C20:1n-9cis   <2% <0.4% 0.2% C20:4n-6cis C20:4w3C20:5n-3cis (EPA) C21:5w3 C22:0  2–5% <0.5% C22:1n-9cis C22:5n-3cisC22:5n-6cis C22:6n-3cis (DHA) C24:1n-9cis Total Saponifiables 99.5%100.3% Oil content % wt/wt Oil $CDN/MT Seed $CDN/MT Seed Oil ContentPhytosterols Brassicasterol Campesterol Stigmasterol β-SitosterolΔ5-Avenasterol Δ7-Avenasterol Δ7-Stigmasterol Tocopherols α β γ δ TotalUnsaponifiables

Trace amounts of the following resin acids and phospholipids were alsomeasured in flax, sesame, canola, mustard, sunflower, cotton, castor,soya, hemp and linseed:

Resin Acids

-   -   Abietic (C20H30O2)    -   Dehydroabietic (C20H28O2)    -   Palustric (C20H30O2)    -   Isopimaric (C20H30O2)    -   Neoabietic (C20H30O2)    -   Pimaric (C20H30O2)

Phospholipids

-   -   N-acylphosphatidylethanolamine    -   phosphatidic acid    -   phosphatidylethanolamine    -   phosphatidylcholine    -   phosphatidylinositol    -   lysophosphatidylcholine

TABLE 2A Typical Hydrocarbon Properties Crude Tall Oil Fatty Acids(CTOFAs) CTOFA (Primary Components Emulsifier) Myristic (n-Tetradecoicacid) (C14:0) Palmitic (Hexadecanoic) (C16:0) 0.10% Palmitoleic (C16:1)Margaric Heptadecanoic (C17:0) cis-10Heptadecenoic Acid Stearic(n-Octadecanoic Acid) (C18:0) 2.00% trans-11 Octadecenoic Acid (C18:1)Ricinoleic Acid (glyceryl tricinoleate) C 18:1-OH Oleic (C18:1n9c)50.00% Linoleic (C18:2n6c) 45.00% Alpha Linolenic (C18:3) GammaLinolenic (C18:3n6) Linolenic Acid (C18:3n3) Stearidonic (C18:4)9,10-dihydroxy-octadecanoic acid (C19) Arachidic (n-Icosanoic Acid)(C20:0) Eicosenoic (C20:1) cis-11,14-Eicosedienoic Acid (C20:2) Gadoleic(C20:4) Behenic (n-Docosanoic Acid) (C22:0) Erucic (Docosenoic) (C22:1)Docosadienoic (C22:2) Lignoceric (n-Tetracosanoic Acid) (C24:0) Nervonic(C24:1) 97.10% Total Resin Acid 25.00% of total FA fraction is resinacid Abietic (C20H30O2) 32.00% Dehydroabietic (C20H28O2) 29.00%Palustric (C20H30O2) 12.00% Isopimaric (C20H30O2) 11.00% Neoabietic(C20H30O2) 4.00% Pimaric (C20H30O2) 2.00%Drilling Fluid Preparation

As is known to those skilled in the art, drilling fluids may becomprised of a wide range of compounds including both a water and oilphase, emulsion stabilizers, seepage control agents, viscosifiers,torque and drag reducing agents, dispersing agents and filtrationcontrol agents.

In accordance with one embodiment of the invention, whole oilseeds maybe added to the drilling fluid at a concentration of 3 kg/m³ to 150kg/m³ to engineer the properties of the drilling fluid.

Examples

With reference to Table 3 and FIG. 1, the effectiveness of adding wholeoilseeds as a means to alter the properties of a drilling fluid wasinvestigated.

Field-tested invert drilling fluids (samples 1-4) with and without aseepage control agent and with and without oilseeds were compared. Eachsample included a base field-tested drilling fluid comprising inter aliaan organophilic clay, water, crude tall oil fatty acids, nonyl-phenylethoxylate, barite and calcium chloride. The base drilling fluid (Sample#1) was prepared in accordance with procedures known to those skilled inthe art and is representative only of a typical drilling fluid.

Sample #2 included the base drilling fluid as well as a known seepagecontrol agent formulation comprising calcium carbonate poultry grit,calcium carbonate fines and calcium carbonate (325 Mesh).

Sample #3 included the base drilling fluid as well as a mixture ofoilseeds including canola, mustard and flax seeds.

Sample #4 was identical to sample #2 but included additional crushedcanola seed.

Each formulation was subjected to laboratory testing in which the fluidproperties of each sample were examined.

TABLE 3 Effect of Oilseeds on Drilling Fluid Parameters MeasuredParameter Cell Cell + Cell + Cell + Sample # Units Base Mud #1 CaCO3 #2Seed #3 Seed #4 Canola Seed (kg/m³) 14.25 14.25 Mustard Seed (kg/m³)14.25 14.25 Flax Seed (kg/m³) 14.25 14.25 Canola Crushed (kg/m³) 14.25Mustard Seed (kg/m³) Flax Seed (kg/m³) Calcium Carbonate Poultry Grit(kg/m³) 14.25 Calcium Carbonate Fine (kg/m³) 14.25 Calcium Carbonate 325Mesh (kg/m³) 14.25 Hot Rolled Hrs 18 25 18 25 Hot Rolled ° C. 121 121121 121 Rheology Temperature ° C. 50 50 50 50 θ 600 ( ) 75 79 73 80 θ300 ( ) 47 45 44 49 θ 200 ( ) 35 34 33 36 θ 100 ( ) 21 22 21 23 θ 6 ( )7 7 7 9 θ 3 ( ) 5 6 5 7 θ 3 @ 10″ ( ) 8 10 8 9 θ 3 @ 10′ ( ) 9 17 9 12 n( ) 0.67 0.81 0.73 0.71 k N · s/m² 0.34 0.14 0.22 0.29 Plastic ViscositymPa · s 28 34 29 31 Yield Point Pa 9.5 5.5 7.5 9 PV/YP Ratio 3 6 4 3 Gel10 Seconds Pa 4 5 4 4.5 Gel 10′ Minutes Pa 4.5 8.5 4.5 6 Fluid Densitykg/m³ 1100 1124 1078 1071 Emulsion Stability @ 30° C. volts 1050 9501150 1260 ES Variation from Base Fluid % −9.52% 9.52% 20.00% HT-HPFiltrate @ 165° C. & ml 12 14 9 8 500 psi Oil/Water Ratio 80/20 80/2080/20 80/20DiscussionSample #2—Addition of Known Seepage Control Agent

As expected, the introduction of calcium carbonate caused adeterioration of certain fluid properties including a significantvariation in the PV/YP ratio and a corresponding and detrimentalincrease in 10′ (Minute) gels. The emulsion stability (as measured bythe voltage required to cause current to flow through the emulsion)caused the emulsion to weaken by 10% as expected due to the consumptionof emulsifiers within the system which are consumed by the surface areaof the seepage control agent. Further the HT-HP Filtration increased by16.7%

Sample #3—Addition of Oilseeds

The addition of whole oilseeds produced a smaller variation in the PV/YPratio in the opposite direction to that of sample 2. In addition, anoverall reduction in viscosity was observed and the emulsion stabilityof the drilling fluid was also observed to have been favorably variedwith the addition of these materials. The emulsion stability wasobserved to improve with the addition of oilseeds by a factor of 10%. Asthe surface area of the seeds was comparable to the surface area of thecalcium carbonate particles within sample #2, the expected result of aloss in emulsion stability due to the consumption of emulsifier by thediluting material was not observed to occur. This result was believed tobe caused by the whole oilseeds providing an effective slow release ofadditional emulsifiers through the seed shell wall (i.e., fatty acids)that imparted additional stability to the emulsion (FIG. 1). There wasalso an improvement in HT-HP filtration results which were observed tobe reduced by 25%.

Sample #4—Addition of Crushed Oilseed

Sample #4 was prepared and tested to verify that the fatty acidscontained within the oilseeds were of sufficient concentration to affectthe emulsion stability of a drilling fluid. Sample #4 was prepared fromsample #3 to which crushed canola seed was added. The evidence of theoilseed effect was immediately verified as the fluid parameters wereaffected. Interestingly, the negative effects of the comminutedmaterial, i.e. the seed hull detritus affected the properties of thefluid in a negative way as evidenced by the increases measured using theΘXXX reading between Θ600 and Θ3. In summary, FIG. 1 shows that theaddition of whole oilseeds favorably reduces the relative viscosity ofthe drilling fluid at increasing shear rates. A further reduction of11.1% in HT-HP was observed.

Other Observations

As shown above, the addition of whole oilseeds to drilling fluidsprovides an effective parameter to enhance the properties of oil basedinvert emulsion drilling fluid.

Other observations in relation to the benefits of using whole oilseedswithin a drilling fluid are detailed below:

The variation in particle size between these seeds allows forengineering of the drilling fluid to adapt to different sizes offractures and other loss zones.

The spherical or flat nature of particular oilseeds provides aneffective mechanical mechanism for the reduction of rotary torque anddrag induced frictional losses.

The oleophilic nature of whole oilseeds minimizes negative effects onthe viscosity of the drilling fluid unlike existing hydrophilicmaterials or crushed oilseeds.

Whole oilseeds do not alter or impede the operation of surface solidscontrol equipment ensuring that fluid maintenance is not impedednegatively during their use. The steady release of high viscosity oilsfrom the whole oilseeds during circulation in the drilling fluid reducesfilter cake permeability, increases the lubricity of the filter cake,increases emulsion stability, and disperses entrained solids. Theaddition of whole oilseeds may be used to lower the specific gravity ofthe drilling fluid as opposed to the use of conventional additives suchas ground limestone that will increase specific gravity. A reduction inspecific gravity will reduce the circulating density or specific gravityof the drilling fluid, which can reduce seepage losses by reducing thehydrostatic pressure of the fluid column (the “chip hold down effect”),as well as increasing drilling penetration rates. It should be notedthat comminuted oil seeds will also reduce the specific gravity ofdrilling fluid, but the viscosity effects will result in increases inpressure needed to circulate the fluid and a corresponding increase inthe Equivalent Circulating Density (ECD) of the drilling fluid, thusnegating the fluid weight reduction imparted by the seed material.

In all cases listed above, the use of oilseeds provides for a low costcontributive effect to the overall benefit of the drilling fluid,replacing or reducing the requirement for expensive refined chemicalsusually required.

The variation in fatty acid constituents of oilseeds allows for theengineering of emulsifiers in an invert emulsion drilling fluid byselection of the seed for its fatty acid. i.e. the presence of C-22fatty acids in mustard seed may be a more desirous material in an oilbased drilling fluid treatment than the use of C-18 from canola or flaxseeds.

The addition of the whole seeds to the oil based drilling fluid systemsdid not result in an increase in the viscosity of the continuous phaseas evidenced with sample #3. Normally the addition of cellulosematerials and calcium carbonate materials results in a change in theviscosity of the continuous phase and thus places a limit on materialaddition based on the capability of the pumping system to circulate adrilling fluid slurry. The whole seeds did not have this effect meaningthat significantly higher (up to 150 kg/m³) concentration levels can beachieved. It should be noted that even the small amount of crushed seedadded in sample #4 had a significant effect on increasing fluidviscosity from sample #3 which had a lower viscosity than the base fluidof sample #1 to a higher viscosity then sample #1.

Highly unsaturated fatty and resin acids caused high degrees of oilwetting in oil based drilling fluids and saturated fatty acids greatlyimproved the performance of oil based muds (OBMs). Thus, the use ofseeds with high amounts of unsaturated fatty acids would be used todisperse or oil wet the solids in OBMs and seeds with more saturatedfatty acids would be used to increase emulsion strength and improveorganophilic clay performance.

Crushed Oilseeds

As shown in Tables 2 and 2A, oilseeds contain a broader range of fattyacids than CTOFAs. As a result, crushed oilseeds (preferably firstpress) without detritus provide a basis for a broader range of soapswithin an invert emulsion after saponification with a saponifying agentsuch as CaOH (Lime). As a result, by selection of a specific oilseed oilor controlled blending of two or more oils, controlled creation of soapscan be realized to impart specific properties to a drilling fluid whencompared to emulsifiers created from CTOFAs. Moreover, oilseeds areeasily blended within a drilling fluid system and do not requireintermediary dilution or specialized mixing steps.

Further still, the hydrophilic/lipophilic balance (HLB) of oilseeds isbroader than CTOFAs thereby enhancing the ability to create specializedproperties within the drilling fluid.

With reference to FIGS. 2 and 3, the effect of adding crushed mustardseed to different drilling fluids is shown in three different drillingfluid compositions containing an organophilic clay (Bentone 150). Thedrilling fluids examined included a) 14.25 kg/m³ Bentone 150, b) 14.25kg/m³ Bentone and 14.25 kg/m³ crushed mustard seed and c) 14.25 kg/m³Bentone and 28.5 kg/m³ crushed mustard seed. As shown in FIG. 2, theplastic viscosity increases with increasing crushed mustard seedconcentration and the yield point decreases with increasing crushedmustard seed concentration (combined indication of dispersion affect);in FIG. 3, the shear stress increases with increasing crushed mustardseed concentration thus demonstrating the ability to control theseproperties of the drilling fluid.

Field Testing

In addition to lab testing, various drilling fluids using whole andcrushed seeds were utilized downhole.

During field trials, it was observed that the addition of whole seedsand crushed seeds (independent additions) caused a reduction in rotarytorque, namely the amount of energy required to turn the drill pipesduring the drilling process as measured by appropriate torque sensors.In addition, an up to 80% drop in the drag or force required to lift orlower the drill pipes out of the hole was observed as measured byappropriate drag weight sensors.

It was also observed that the addition of crushed seeds to the drillingfluid caused an immediate reduction in high temperature/high pressure(HT-HP) filtration just as with the whole seeds as determined inaccordance with American Petroleum Institute (API) methodologies.

Table 4 shows a comparison between drilling fluid cost data for sixwells drilled with conventional drilling fluids and two wells drilledwith drilling fluids incorporating oilseeds. As can be seen, in thewells drilled using drilling fluids with oilseeds, there was significantreduction in total drilling fluid costs compared to drilling fluid costsfor comparable wells drilled without oilseeds. In each well the primaryemulsifier was CTOFAs and the secondary emulsifier was a polyamide. Allwells were drilled in the same geographic location.

TABLE 4 Field data showing drop in product consumption when oil seedsused in OBM Product Usage without Oil Seeds Site 1 Site 2 PrimaryEmulsifier 68 33 Secondary Emulsifier 68 39 Bentone 150 102 0 Oil(Losses) 90 m³ 104 m³ Programmed cost $200,000 $200,000 Total Cost$198,573.47 $153,478.04 Site 3 Site 4 Primary Emulsifier 108 64Secondary Emulsifier 68 64 Bentone 150 90 136 Oil (Losses) 93 m³ 110 m³Programmed cost $200,000 $200,000 Total Cost $160,562.45 $180,724.70Site 5 Site 6 Primary Emulsifier 75 41 Secondary Emulsifier 52 36Bentone 150 42 10 Oil (Losses) 208 m³ 100.5 m³ Programmed cost $200,000$200,000 Total Cost $253,726.02 $193,750.45 Product Usage with Oil SeedsSite 7 Site 8 Primary Emulsifier 41 15 Secondary Emulsifier 40 11Bentone 150 0 4 Oil (Losses) 54 m³ 70 m³ Programmed cost $200,000$200,000 Total Cost $131,000 $120,000

1. A method of altering the properties of a drilling fluid comprisingthe step of adding an effective amount of crushed or whole oilseeds or amixture of crushed or whole oilseeds to a drilling fluid, the crushed orwhole oilseeds or mixture of crushed or whole oilseeds selected toimpart any one of or a combination of: an increase in drilling fluidemulsion stability in oil-based or invert emulsion fluids, decreasedspecific gravity of the drilling fluid, seepage loss control, filtrationcontrol, oil wetting, deflocculation/dispersion of entrained solids,reduced drag and rotary torque reduction.
 2. A method as in claim 1wherein the oilseeds are selected from any one of or a combination ofcanola, flax, sunflower, cotton, castor, soya, hemp, safflower, grape,palm kernel, lesquerella, corn, peanut, mustard, poppy, sorghum, andsesame seeds.
 3. A method as in claim 1 wherein the oilseeds are addedto a concentration of 3-150 kg/m³ of drilling fluid.
 4. A method as inclaim 3 wherein the oilseeds are added to a concentration of 10-60 kg/m³of drilling fluid.
 5. A method as in claim 3 wherein the oilseeds areadded to a concentration of 45 kg/m³ of drilling fluid.
 6. A method asin claim 1 wherein the whole oilseeds or a mixture of whole oilseeds isadded to the drilling fluid immediately prior to circulating thedrilling fluid downhole.
 7. A method of stabilizing a drilling fluidemulsion comprising the step of adding an effective amount of wholeoilseeds or a mixture of whole oilseeds to a drilling fluid emulsion. 8.A method as in claim 7 wherein the oilseeds are selected from any one ofor a combination of canola, flax, sunflower, cotton, castor, soya, hemp,safflower, grape, palm kernel, lesquerella, corn, peanut, mustard,poppy, sorghum, and sesame seeds.
 9. A method as in claim 7 wherein theoilseeds are added to a concentration of 3-150 kg/m³ of drilling fluid.10. A method as in claim 7 wherein the oilseeds are added to aconcentration of 10-60 kg/m³ of drilling fluid.
 11. A method as in claim7 wherein the oilseeds are added to a concentration of 45 kg/m³ ofdrilling fluid.
 12. A method as in claim 7 wherein the crushed or wholeoilseeds or a mixture of crushed or whole oilseeds is added to thedrilling fluid immediately prior to circulating the drilling fluiddownhole.